At present, mobile phones and smart phones are widespread. With increasing use of mobile phones and smart phones, resources in a base station (eNB: evolved Node B) or a core network may become insufficient due to simultaneous outgoing calls from mobile stations (UE: User Equipment) and congestion may occur. Thus, restriction control is introduced into an LTE (Long Term Evolution) network to restrict an access request from a mobile station.
According to typical restriction control, an access class (AC) is assigned to every mobile station camping on a base station and transmission of a connection request signal from a mobile station is controlled based on the access class. For example, the base station transmits an access class for restriction control and a restriction control parameter (a restriction rate, a restriction time, or the like) as broadcast information (SIB2: System Information Block 2) to the mobile station. When the mobile station receives the broadcast information, the mobile station determines whether the mobile station is subject to restriction control and stops a request for connection to the base station when the mobile station is subject to restriction control (see 3GPP TS 36.331, V12.1.0 (2014-03)).
In 3GPP (The 3rd Generation Partnership Project), four types of restriction control: ACB (Access Class Barring), SSAC (Service Specific Access Control), ACB for CSFB, and EAB (Extended Access Barring) are defined. ACB is restriction control for every packet call and is triggered to reduce congestion on resources in radio (eNB) or an MME/S-GW (Mobility Management Entity/Serving Gateway). SSAC is restriction control for MMTEL Voice (VoLTE: Voice over LTE) and MMTEL Video and is triggered to reduce congestion on resources in radio (eNB) and an IMS (IP Multimedia Subsystem) node. ACB for CSFB is restriction control for CSFB (Circuit Switched Fall Back) calls and is triggered to reduce congestion on resources in radio (eNB) caused by the CSFB calls. EAB is restriction control for MTC (Machine Type Communication) terminals and is triggered to reduce congestion on resources in radio (eNB) caused by the MTC terminals.